James B. Eisenkraft

Oxygenation and hemodynamic changes during one-lung ventilation: Effects of CPAP10, PEEP10, and CPAP10/PEEP10

The effects of 10 cm H2O positive end-expiratory pressure (PEEP10), 10 cm H2O continuous positive airway pressure (CPAP10), and their combination (CPAP10/PEEP10) on oxygenation and hemodynamics were studied in 20 patients undergoing one-lung ventilation (OLV) with 50% nitrous oxide, isoflurane, and oxygen. Compared to OLV alone, CPAP10 and CPAP10/PEEP10 significantly increased PaO2 (from 80 +/- 6 to 125 +/- 11 and 137 +/- 17 mmHg, respectively); increased SaO2 (from 93.9 +/- 0.8 to 97.1 +/- 0.5 and 97.0 +/- 0.6%, respectively); and decreased Qs/Qt% (from 36.4 +/- 1.6 to 26.2 +/- 2.0 and 23.2 +/- 2.0%, respectively). Although not statistically significant, PEEP10 caused an increase in PaO2 (to 105 +/- 12 mmHg) and a decrease in Qs/Qt% (to 27.6 +/- 2.1%), which are of clinical significance. However, CPAP10/PEEP10 caused a significant decrease in cardiac output (from 4.50 +/- 0.26 to 3.83 +/- 0.22 L/min), stroke volume (58.6 +/- 3.0 to 52.8 +/- 2.9 mL/beat), and oxygen delivery (653 +/- 39 to 590 +/- 38 mL/min). Application of CPAP10, PEEP10 or their combination had no significant effect on heart rate, arterial, pulmonary arterial, mean pulmonary capillary wedge or central venous pressures, systemic or pulmonary vascular resistances, or mixed venous oxygen saturation. Overall, CPAP10 had the most beneficial effect on oxygenation and hemodynamics during OLV with 50% N2O, isoflurane and oxygen.

Sensitivity to vecuronium in myasthenia gravis : a dose-response study

A cumulative dose plus infusion technique and integrated EMG monitoring of the first dorsal interosseous muscle were used to determine the potency of vecuronium in 20 normal patients and in ten patients with myasthenia gravis under thiamylal, N2O, O2, fentanyl anaesthesia. The mean (± SEM) values for ED50, ED90, and ED95 in the normal patients were 19 ± 1, 31 ± 1 and 36 ± 2 μg · kg− 1, respectively. Myasthenic patients showed increased sensitivity to vecuronium, the mean values for ED50, ED90, and ED95 were 10 ± 2, 17 ± 2 and 20 ± 3 μg · kg− 1, being50, 55 and 56 per cent of normal, respectively. We did not demonstrate a difference in sensitivity to vecuronium between those myasthenic patients who received pyridostigmine preoperatively and those who did not, nor among those chronically treated with corticosteroids, compared with those who were not.RésuméUne dose cumulative plus une technique de perfusion et une surveillance électromographique intégrée du muscle interosseux dorsal fut utilisée afin de déterminer la puissance du vécuronium chez 20 patients normaux et chez dix patients atteints de myasthénie grave sous thiamylal, N2O, O2, et fentanyl. Les valeurs moyennes (± SEM) du ED50, ED90 et ED95 chez les patients normaux étaient de 19 ± 1, 31 ± 1 et 36 ± 2 gmg · kg− 1 respectivement. Les patients myasthéniques ont démontré une augmentation de la sensitivité au vécuronium, les valeurs movennes de la ED50, ED90 et ED95 furent 10 ± 2, 17 ± 2 et 20 ± 3 μg · kg− 1 étant respectivement 50, 55 et 56 pour cent de la normale. On n’a pas démontré de différence avec les patients avant reçu de la pyridostigmine en période préopératoire et ceux qui n’en n’ont pas reçue, de même qu’on n’en a pas trouvé avec ceux qui étaient traités aux corticostéroīdes comparé à ceux qui ne l’étaient pas.

Positive end-expiratory pressure during one-lung ventilation improves oxygenation in patients with low arterial oxygen tensions

OBJECTIVE The application of 10 cm H2O of positive end-expiratory pressure (PEEP10) to the ventilated lung during one-lung ventilation (OLV) has an unpredictable effect on PaO2. It was hypothesized that patients with a low PaO2 (< 80 mmHg) during OLV may benefit from application of PEEP. DESIGN Prospective, open. SETTING A university medical center. PARTICIPANTS Eighteen patients were studied who were undergoing OLV for pulmonary resection. All were anesthetized with thiamylal, N2O/O2 (50%/50%), isoflurane, and pancuronium. INTERVENTIONS Application of PEEP10 during one-lung ventilation. MEASUREMENTS AND MAIN RESULTS Hemodynamics and oxygenation were measured during two-lung ventilation in the lateral position, OLV, and OLV plus application of PEEP10. Overall, PEEP10 during OLV failed to produce significant changes in PaO2, Qs/Qt%, cardiac output (CO), SvO2, or mean arterial pressure. However, in 11 patients whose PaO2 was less than 80 mmHg during OLV, application of PEEP10 significantly increased PaO2, decreased Qs/Qt%, and decreased CO (p < 0.05). In the 7 patients whose PaO2 was greater than 80 mmHg on OLV, the authors did not find a significant effect of PEEP10 on the hemodynamic or oxygenation parameters measured. CONCLUSIONS In patients with a low PaO2 (< 80 mmHg) during OLV with F1O2 = 0.5, PaO2 is increased by the application of PEEP10. This maneuver may be useful in situations in which application of continuous positive airway pressure (CPAP) to the nonventilated lung is not possible.

A defasciculating dose of d-tubocurarine causes resistance to succinylcholine

Forty-four patients, ASA physical status I or II, undergoing thiamylal, fentanyl,N2O/O2 anaesthesia were studied to determine the dose-response to succinylcholine (Sch) without prior defasciculation (24 pt —Group I), or three minutes following d-tubocurarine (dTC), 0.043 mg · kg−1 (20 pt —Group 2). The individual log dose-logit response curve for each patient was determined using a cumulative dose plus infusion technique and integrated EMG monitoring of the first dorsal interosseous muscle. The mean (±SEM) ED50, ED90 and ED95 values for Sch in Group I were 0.13 ±0.01, 0.19 ±0.01 and 0.22 ±0.01 mg · kg−1, and in Group 2 were 0.16 ±0.01, 0.25 ±0.01 and 0.29 ±0.02 mg · kg−1, respectively. The mean ED values in Group 2 were significantly greater than the equivalent values in Group 1 (P < 0.05). Compared with values in Group I, ED values in Group 2 represented mean increases of 23, 32, and 32 per cent, respectively. These pharmacodynamic data indicate that the dose of Sch needs to be increased by 32 per cent following a defasciculating dose of dTC 3 mg · 70 kg−1 (0.043 mg · kg−1).RésuméLors d’ une anesthésie au thiamylal, fentanyl et N2O, nousavons évalué la courbe dose-réponse de la succinylcholine (Sch) de 24 patients sans précurarisation (groupe 1) et celle de 20 autres, trois minutes après l’injection de 0,043 mg · kg−1 de d-tubocurarine (groupe 2). Les mesures individuelles combinaient le logarythme de la dose cumulative (infusion continue) au logit de la dépression de l’EMG du premier muscle interosseux dorsal. Les DE50, DE90 et DEg95 (moyenne ±erreur-type) de la Sch étaient respectivement dans le groupe I de: 0,13 ±0,01, 0,19 ±0,01 et O,22 ±0,01 mg · kg−1 alors que dans le groupe 2 elles étaient de: 0,16 ±0,01, 0,25 ±0,01 et O,29 ±0,02, supérieures done à celles du groupe 1 de 23, 32 et 32 pour cent respectivement (P < 0,05). Grâce à cette étude pharmacodynamique, on voit qu’il faut augmenter la dose de Sch de 32 pour cent si on la fait précéder d’une dose de 3 mg · 70 kg (0,043 mg · kg−1) de d-tubocurarine.

Potential for barotrauma or hypoventilation with the Dräger AV-E ventilator.

The system pressure relief valve of the Dräger AV-E anesthesia ventilator is powered by connecting tubing from the ventilator. In this case, the tubing became kinked when the anesthesia machine was moved. This resulted in an iatrogenically induced valve malfunction and increasing minimum and peak pressures in the patient circuit. A laboratory study was performed to evaluate the effects of kinking the connecting tubing. The potential for producing barotrauma or hypoventilation with this design of ventilator is discussed. Repositioning the anesthesia machine after a satisfactory check may precipitate a hazardous situation. An anesthesia machine should be checked out in the final position in which it is to be used.

Performance of erroneously filled sevoflurane, enflurane and other agent-specific vaporizers

Objective. Erroneous filling of an agent-specific anesthesia vaporizer may result in concentration and potency outputs that are very different from those expected from the concentration dial setting. Enflurane and sevoflurane have relatively similar saturated vapor pressures (SVPs 175 mmHg and 160 mmHg, respectively, at 20°C) and potencies (MACS 1.68% and 2%, respectively). We derived an equation to relate the vapor concentration output of an agent-specific vaporizer to the gas inflow splitting ratio (SR) created by the vaporizer and the SVP of the potent inhaled agent.Methods. To test the validity of this equation, we filled an Enfluratec 4 enflurane vaporizer with sevoflurane and a Penlon PPV Sigma sevoflurane vaporizer with enflurane and compared the vapor concentration outputs with our predictions.Results. The equation accurately predicted the vapor concentration outputs of the erroneously filled enflurane and sevoflurane vaporizers. The potency (MAC) output of the erroneously filled Enfluratec 4 vaporizer decreased by 22%–33%, and that of the Penlon PPV Sigma sevoflurane vaporizer increased by 21%–31% from those expected from the concentration dial settings.Conclusion. When an agent-specific variable bypass vaporizer is erroneously filled, the vapor concentration outputs can be predicted from the splitting ratio created by setting the vaporizer concentration dial and the SVP of the agent.